1. Field of the Invention
The present invention relates to novel, improved filled polymeric, especially filled elastomeric compositions, and, more especially, to such filled compositions comprising a matrix/filler interfacing additive which comprises the reaction product of at least one polyamine with at least one carboxylic acid.
2. Description of the Prior Art
It is of course well known to this art that the problem of reinforcing polymeric materials with inorganic fillers is both complex and difficult. On the one hand, the reinforcing filler must be thoroughly dispersed in the polymer matrix, while on the other hand good bonding must be obtained between the filler and the polymeric material. Furthermore, the reinforcement must be carried out economically, without entailing any secondary disadvantage during handling, such as toxicity. This explains why a large number of solutions have been proposed to the art, often specific to a particular filler and particular polymer, taking into account various factors such as the matrix of the polymer, the nature of the possible chemical bonds, and the surface chemistry of the filler. Coupling agents are being studied at the present time. Of these, special mention should be made of the family of silanes and particularly the mercaptosilanes. This has been described in the literature, particularly in Rubber World, October 1979, pages 53-58 and in European Rubber Journal, March 1979, pages 37-46.
Unfortunately, the use of silane coupling agents has encountered two serious disadvantages: firstly, their cost, which under existing conditions is very high relative to that of the filler proper, and, secondly, their odor, which virtually prevents their use beyond the threshold of 1% by weight relative to the polymer.
Our U.S. Pat. No. 4,322,336 features improving the compatibility of plasticizers and reinforcing fillers in polymers, employing additives based on alkenyl succinimides.
Also, our U.S. Pat. No. 4,348,311 features a filler reinforced elastomer, and comprising a coupling agent therefor, such coupling agent including at least one silane and at least one succinimide per our '336 patent.
This latter technique affords excellent results as compared with silanes used alone, but uses a small enough quantity of silanes, substantially without giving rise to the disadvantage inherent in same. And unlike carbon black, the precipitated silicas which impart a considerable degree of reinforcement have the disadvantage of making rubber mixtures too viscous. The main reason for the high viscosity is the strength of the silica network which is established in the rubber [A. Voet and J. C. Morawski, Rubber Chem. Technical, 47, 4, pp. 765-777 (1974)].
Indeed, our experimentation has demonstrated that for such network to be weakened, the interaction among the particles thereof has to be reduced.